Acute lung injury in the intensive care unit is treated with administration of high inspired oxygen tensions which can be toxic to the lung. Pulmonary oxygen toxicity is generally attributed to the excessive production of reactive oxygen intermediates (RO1), e.g., superoxide (O2), hydrogen peroxide (H2O2), and hydroxyl radicals. Recently nitric oxide (NO) is being used to treat hyperoxic lung disease, but its effect is variable and its role remains controversial. We hypothesize that selective modulation of NO/RO1 in different cellular compartments regulates tissue responses to hyperoxia. In this proposal, we will employ state of the art adenoviral gene transfer technique in vitro and in vivo. The transgenes we have selected for these studies are neuronal nitric oxide synthase (nNOS), extracellular superoxide dismutase (ECSOD), and arginases I and II (AI and AII). Overexpression of these four genes are expected to affect NO and reactive oxygen intermediates (RO1) production in different cell compartments: nNOS (yields intracellular NO/yields 02-), ECSOD (yields extracellular NO/yields 02-), and AI and AII (yields intracellular NO/yields O2-). We will determine how these transgenes modulate, oxidative/nitrosative stress, and NO/ROI mediated inflammation, cellular proliferation, and apoptosis. The specific aims of this proposal are 1) characterize the transgene expression of nNOS, ECSOD, AI, and AII in vitro 2) characterize intratracheal adenoviral gene transfer in normal rabbit lung and 3) evaluate how adenoviral mediated transgenes nNOS, ECSOD, AI, and AII modulate effect of NO in hyperoxia. These studies should not only better unravedl the basic mechanisms of hyperoxic lung injury, but also provide a rationale basis for therapeutic gene transfer using NO. Ultimately we are hopeful that these results may also extend to other oxidant injuries in the lung.